A double-decker bus has overturned, leaving dozens of people injured.
The Stagecoach South West service was travelling from Torquay to Plymouth when it crashed on the A385 between Totnes and Paignton in Devon at about 11:00 BST.
Police said up to eight people had been seriously hurt and were undergoing assessment.
A total of 37 people are currently being treated at several hospitals around Devon, according to the NHS.
The emergency services closed the road and a major incident was declared, which has now been "stood down".
Uninjured passengers were taken to Paignton bus station for support and help to continue their journeys.
Jane Viner, chief nurse and deputy chief executive at Torbay and South Devon Foundation Trust, said many NHS staff had come in on their day off to help deal with the casualties.
She said: "It's been a huge team effort by emergency services and hospital staff in Exeter, Plymouth and Torbay - we've had extra surgeons, doctors, GPs, nurses, chaplains and many other support staff reporting for duty. Thank you all."
The road will stay shut in both directions for several hours for "investigation and recovery", said Gerald Taylor, the area manager for Devon & Somerset Fire and Rescue Service.
Police said the bus driver had not been arrested, confirming he was assisting them with their inquiries.
A witness said: "It's like nothing you've ever seen up here, there's emergency vehicles everywhere."
A spokesman for Stagecoach South West said the company was helping emergency services and its thoughts were with the victims of the crash.
"Safety is our absolute priority and we will be assisting the investigation into the circumstances involved in the incident," he added.
Several ambulances were sent to the scene, as well as the air ambulance.
The Liberal Democrat MP for Totnes, Sarah Wollaston, thanked the emergency services for their efforts under difficult circumstances.
Dreadful news, thank you to all our emergency services responding in difficult conditions. https://t.co/XXJMDBc8xs— Sarah Wollaston MP (@sarahwollaston) October 5, 2019